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March 27th, 2012, 05:46 PM   #1
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Prove the difference between numbers

The sum of the digits of a two-digit prime number is subtracted from the number. Prove that the difference cannot be a prime number.
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March 27th, 2012, 06:47 PM   #2
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Re: Prove the difference between numbers

Let A be the tens place digit and B be the units digits, the the difference is:



Since 9 is composite, so must 9A be composite.
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